Solar panel types explained

Almost every residential solar panel is one of three families: monocrystalline silicon, polycrystalline silicon, or thin-film. They convert sunlight to DC electricity the same way, but they differ in efficiency, appearance, and how much roof area you need. Here is what separates them.

Monocrystalline

Monocrystalline ("mono") cells are sliced from a single continuous silicon crystal. That uniform structure gives them the highest efficiency of the common types — mainstream residential mono panels typically land in the low-to-mid 20% range — and a solid black look many homeowners prefer. Because each panel produces more watts per square foot, mono is the default when roof space is limited.

Most modern mono panels use one of several cell architectures (PERC, TOPCon, or heterojunction), which affect efficiency and temperature behavior. Always read the specific module datasheet rather than assuming.

Polycrystalline

Polycrystalline ("poly" or multicrystalline) cells are cast from melted silicon that solidifies into many crystals. The result is a bluish, marbled cell and slightly lower efficiency than mono of the same generation. Poly panels were historically cheaper per watt, which drove their popularity, but the price gap has narrowed and new residential installs have shifted heavily toward mono. Poly still appears in some budget and utility-scale contexts.

Thin-film

Thin-film panels deposit a very thin photovoltaic layer — such as cadmium telluride (CdTe), copper indium gallium selenide (CIGS), or amorphous silicon — onto glass, metal, or a flexible backing. They are lightweight, flexible in some forms, and tend to hold output better in high heat and diffuse light. The trade-off is lower efficiency, so a thin-film array needs more area for the same rating. That makes it common in large ground mounts and specialty applications, but uncommon on space-constrained residential roofs.

Comparing the three

Efficiency ranges shift as technology improves, so treat these as orientation, not gospel.

What actually matters for a design

For a permit-ready residential design, the panel type matters less than the numbers on its datasheet: rated power, module Voc and temperature coefficient (which drive string voltage limits), Isc, dimensions, and weight. Those values feed directly into PV string sizing under NEC 690.7 and your structural load check. A high-efficiency mono panel and a larger poly panel can produce the same array output — they just occupy different amounts of roof.

Because temperature coefficient varies by cell technology, two "same wattage" panels can size into different string lengths in a cold climate. This is exactly the kind of spec you confirm against the manufacturer datasheet before finalizing a layout.

Whatever type you choose, a licensed electrician or PE must review the final design. Panel technology is only one input — see how the rest of the package comes together in what's in a solar permit set.

Educational reference, reviewed 2026-07. A design aid, not a substitute for a licensed electrician or PE. Confirm the enforced NEC edition and local amendments with your AHJ.